The Gates BC1H

In my never ending fascination with broadcast transmitters, I bring you the Harris/Gates BC1H. This is an updated model of the BC1G, the main difference being the solid state audio and oscillator sections in the later H model. This design uses the simple 833 parallel final and 833 push pull modulator

Sales brochure, click to down load the four page .pdf

Harris/Gates BC1H AM transmitter

Schematic:

Gates/Harris BC1H overall schematic diagramHarris/Gates BC1H

Harris/Gates BC1H Transmitter running at 1,000 watts into the antenna. Like many old tube transmitters, this sounds great on the air. The transmitter was made in 1975 and is in backup service. For a 37 year old transmitter, it runs like a champ and comes on consistently. Like the preceding Gates BC-1 models, this transmitter is rugged and reliable. My only comment is the transistors in the solid state driver section are no longer available. If that were to become an issue, one can always look up the tube audio driver from previous versions (T and H models). It would be a shame to throw away a good transmitter for lack of a couple of transistors, but I know some who have done just that.

14 thoughts on “The Gates BC1H”

I down loaded the pdf file of that transmitter brochure for the sake of fun and fascination that I have with these things. When able,…let’s see some down loadable brochures of old Collins and Continental transmitters. I have taken a huge interest in
Collins and Continental transmitters in a big way.

Had both a BC-1H and a BC-1T at the same site in Florida in the early 1970’s. I have a suggestion for engineers looking for parts for older transmitters. If you
can remember stations that had the model there is a good chance that although the transmitter may gone I’ll bet an envelope of spare transistors and other parts
may be lurking somewhere on a shelf under a bunch of crap. I saw this all the time. Back in the 70’s and 80’s when an engineer sold a transmitter they would carefully
gather up all the books and spare parts. Latter days of the industry saw equipment shoved out the door little thought and no one interested in taking time to bother with incidentials.
On the chance there is an engineer servicing the facility it may be worth a try.

Dewey, Collins and Continental transmitters were probably some of the best designed of all time. Collins equipment especially power supplies were designed to government specs. Two of my favorite transmitters of all time were the Collins 830 series 10 KW FM and the 21E 5 KW AM. Both built like a BSH

FYI the early 1H had the 807 tube driver board, the later 1H1 had the transistor driver board. I don’t think there were many with the tube driver sold as most but not all that I have seen have the solid state board.

I think this was the last AM 1KW tube transmitter that Harris manufactured.
The next model was the MW 1. Paul I mantained that very transmitter for twenty three years
changed out the PCB caps in the power supply. Recaped the audio driver board. that transmitter always sounded great. It was never as loud as the SX1A that is there but the audio always sounded smoother at least to my ears. I had that transmitter running c quam
stereo back in the day peformed very well nice separation.

@Dewey, I will keep my eyes open for collins/continental information
@Chris, I have looked around at a few transmitter sites that formerly used BC5H and BC10H transmitters (which used the same audio board) and have not been lucky enough to find the driver transistors. However, I will keep my eyes open.
@Bill, I was not aware of 807 drivers in the H model transmitters. The main difference between the T/G and the H models is the arrangement of the 833A tubes. The T/G’s had them in a line along the left side, the H’s have them along the front. Schematically, all of these transmitters are very similar.
@Ed, You will be happy to know, this rig still sounds great. I ran it into the antenna for about 1/2 hour last Friday.

Drop in replacement for the driver transistors… BU426(A), BUW11(A) or 2SC3550.

I’ve upgraded a half dozen of these beasts. That transmitter had absolutely beautiful audio, rock solif when adequately cooled and would heat the studios in the winter time without having to turn on the furnace.

You had to keep it behind a couple of walls because it’s a growler and will make you nuts.

I have one sitting in my garage, a freebie from a local AM that wanted to update. Poor guy emails me about once a month crying about how terrible their audio is now.

Mike,
The 10H is fairly conventional, a solid state push-pull audio driver feeding the grids of the modulator tubes, which load into the modulation transformer. The audio driver also develops a -250V grid bias for the modulators.
99% of the time the audio driver has failed transistors or a bad power supply.
Do you have competent engineering help available? If not, I’m sure a few of us could provide names of people in your area.